Oil has plunged around $15 a barrel over the past month but gasoline prices have inched down by just a penny in the same span, with persistently high costs at the pump frustrating both inflation-weary drivers and the White House, which again raised concerns about potential price gouging. Data from the American Automobile Association (AAA) shows national average gasoline prices have fallen from $3.402 a month ago to $3.390 on Nov. 30, or barely over one cent. By contrast, U.S. oil (West Texas Intermediate) futures prices have fallen from around $84 a barrel on Nov. 1 to about $69 a barrel on Dec. 1—a drop of around 19 percent—driving speculation about when cheaper crude will push down prices at the pump. “The recent drop in futures prices could result in a discount of around 25 cents per gallon or more,” Mark Jenkins, spokesman for the AAA, said in a statement, adding …